Chip board and a process for the preparation thereof

ABSTRACT

A chip board including an intermediary layer ( 1 ) and a layer ( 2 ) of large chips positioned on both sides of said intermediary layer. An outer layer ( 3 ) is provided on the 5 outer surface of each layer of large chips. In addition to the chips, the layers include an adhesive. The intermediary layer ( 1 ) includes a mixture of wood chips having chip fractions of a chip size of 0.1 to 20 mm, and the chips of this layer are randomly oriented. The individual chip in the layer ( 2 ) of large chips presents the following characteristics: a length of approx. 50 to approx. 130 mm, a width of approx. 4 to approx. 40 mm and a thickness of approx. 0.2 to approx. 2.0 mm. The chips within each layer ( 2 ) of large chips are all oriented in one and the same direction. As a result, a chip board is obtained which demonstrates a significantly higher E-module and stiffness in flexure than hitherto known despite a reduced consumption of material.

TECHNICAL FIELD

The present invention relates to a furniture chip board as stated in thepreamble of claim 1.

BACKGROUND ART

A chip board is known which has a core layer and an auxiliary layer oneach side of the core layer. The intermediary layer includes wood chipsand a binder, while the two auxiliary layers include chips. A chip boardof this type is not completely satisfactory because the E-module thereofis between 2000 to 3000 N/mm² when it is bent, while the flexuralstrength of said chip board is 10 to 15 N/mm², which is not entirelysatisfactory.

DE 10049050 A discloses a chip board including a core layer and a layerof big chips positioned on both sides of the cover layer. An outer layeris positioned on the outer surface of each layer of big chips. Inaddition to the chips the layers include an adhesive. The core layerincludes a mixture of wood chips having chip fractions of a chip size of0.1 to 10 mm. The chips of the core layer are randomly oriented whilethe individual chip in the layer of big chips presents the followingcharacteristics: a width of 10 to 40 mm, a thickness of 0.40 to 0.85 mm.The chips within the individual layer of big chips are all directed inone direction. This chip board is not a furniture chip board.

DISCLOSURE OF INVENTION

The object of the present invention is to provide a furniture chip boardof the above type, which demonstrates a significantly higher E-moduleand stiffness in flexure than hitherto known despite a reducedconsumption of material.

According to the invention this object is achieved by a furniture chipboard having the features stated in the characterising part of claim 1.

According to the invention, the core layer may include a mixture of woodchips having chip fractions of a chip size of 0.2 to 0.17 mm, while thechips of the layers of big chips may be oriented in one direction,whereby a particularly high E-module is obtained.

According to the invention, each chip of each layer of big chips maypresent the following characteristics: a length of 80 to 110 mm, a widthof 5 to 30 mm, preferably 10 to 20 mm, and a thickness of 0.4 to 1.0 mm.These chip dimensions have turned out to be particularly advantageous.

In addition, according to the invention the chips may be kept togetherby 8 to 15% by weight of adhesive, preferably 10 to 13% by weight ofadhesive, preferably urea-formaldehyde adhesive, i.e. UF adhesive,melamine-urea-formaldehyde adhesive, i.e. MUF adhesive,melamine-urea-phenol-formaldehyde adhesive, i.e. MUPF adhesive,isocyanate adhesive, i.e. PMDI adhesive or tannin adhesive orcombinations thereof. As a result, the chip board is provided with aparticularly good cohesion ability.

An embodiment of the furniture chip board according to the inventionwhere an outer layer is positioned on the outer surface of each layer ofbig chips is characterised in that the outer layers include a chipmixture having chip fractions of a chip size of 0.1 to 10 mm, preferably0.1 to 5 mm. As a result, the stiffness in flexure is particularly high,and the lateral faces of the chip board are fine and obtain a structuresuitable for foiling, application of coating layers or the like.

The present invention also relates to a process for the preparation offurniture chip boards according to the invention as stated in thepreamble of claim 6. This process is characterised in the featuresstated in the characterising part of claim 6. The process has turned outto be particularly advantageous for preparing the furniture chip boardaccording to the invention.

A rigid 12 mm furniture chip board can tolerate the same load as aconventional 18 mm furniture board, such as a bookcase shelf. This ispossible despite a reduced consumption of material.

Finally according to the invention, the furniture chip board may beproduced by means of an intermittent press or by a continuous pressingprocedure, the pressing period being 8 to 13 seconds per mm of thethickness dimension of the furniture chip board.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below with reference to thedrawings, in which

FIG. 1 is a diagrammatic cross sectional view of a furniture chip boardaccording to the invention having a core layer and two layers of bigchips, and

FIG. 2 is a diagrammatic cross sectional view of a furniture chip boardaccording to the invention having a core layer, two layers of big chipsand two outer layers.

BEST MODES FOR CARRYING OUT THE INVENTION

The furniture chip board shown in FIG. 1 includes a core layer 1 and alayer 2 of big chips positioned on both sides of said core layer. Inaddition to the chips, the layers also include an adhesive.

The core layer 1 includes a mixture of wood chips having chip fractionsof a chip size of 0.1 to 20 mm, the chips of the core layer beingrandomly oriented. Each chip of the individual layer 2 of big chips hasa length of approx. 6 to 130 mm, a width of approx. 4 to approx. 40 mmand a thickness of approx. 0.2 to approx. 4.0 mm. The chips of eachlayer 2 of big chips are all oriented in one and the same direction.

The core layer 1 can include a mixture of wood chips having chipfractions of a chip size of 0.2 to 17 mm, the chips in the layers 2 ofbig chips being oriented in the longitudinal direction of the chipboard.

Each chip of the individual layer 2 of big chips can present thefollowing characteristics: a length of 70 to 120 mm, preferably 80 to110 mm, a width of 5 to 30 mm, preferably 10 to 20 mm, and a thicknessof 0.2 to 2.0 mm, preferably 0.4 to 1.0 mm. The chips can be kepttogether by 8 to 15% by weight of adhesive, preferably 10 to 13% byweight, preferably urea-formaldehyde adhesive, i.e UF adhesive,melamine-urea-formaldehyde adhesive, i.e. MUF adhesive,melamine-urea-phenol-formaldehyde adhesive, isocyanate adhesive, i.e.PMDI adhesive or tannin adhesive or combinations thereof.

As shown in FIG. 2, the chip board can include five layers: theinnermost layer being a core layer 1 and on the outer surface thereof alayer 2 of big chips. Two outer layers 3 are then positioned on theouter surface of the layers 2 of chips. These outer layers can include achip mixture having chip fractions of a chip size of 0.1 to 10 mm,preferably 0.1 to 5 mm.

Each furniture chip board can be prepared by means of an intermittentpress or by a continuous pressing procedure at a temperature of 150 to230° C. and a pressure of 20 to 50 bars, the pressing period being 5 to15 seconds per mm of the thickness dimension of the furniture chipboard.

The preparation of a furniture chip board according to the invention caninclude the following steps:

-   -   First, a chip mixture is scattered on a press plate, a wire, or        a scatter band to provide an outer layer 3, then a chip mixture        to provide a layer 2 of big chips, then a chip mixture to        provide a core layer 1, then a chip mixture to provide a layer 2        of big chips and finally a chip mixture to provide an outer        layer 3, every chip of the core layer 1 and optionally of the        outer layers 3 being randomly oriented during the scathing,        while the chips of each layer 2 of large chips being oriented in        one and the same direction during the scattering,    -   The layers are compressed by means of an intermittent press or        by a continuous pressing procedure at a temperature of 150 to        230° C. and a pressure of 20 to 50 bars, the pressing period        being 5 to 15 seconds per mm of the thickness dimension of the        completed furniture chip board.

The components of the furniture chip board can optionally be compressedto such an extent that the chip board achieves a density of 600 to 800kg/m³, preferably 650 to 750 kg/km³.

Subsequent to the pressing, the chip boards are cooled, whereafter theyare optionally polished to obtain a final desired surface structure andto maintain a predetermined thickness tolerance.

EXAMPLE

A chip board was prepared having a density of 700 to 750 kg/m³.

The Bending E-module was measured to be 10,000 to 13,000 N/mm². TheBending E-module for a conventional furniture chip board is in the rangeof 2,000 and 3,000 N/mm².

The flexural strength was measured to be 60 to 90 N/mm² for the rigidchip board compared to the usual 10 to 15 N/mm² for conventionalfurniture chip boards.

In other words, when a 12 mm rigid furniture chip board according to theinvention is produced, it can tolerate the same load as a conventional18 mm chip board, for instance used as a shelf, despite a reducedconsumption of material.

When the thickness of the furniture chip board is maintained, thedistance of support can be increased by 40%, for instance from 700 mm to1000 mm as far as a shelf is concerned.

When the density was in the range of 400 to 500 kg/m³, the resultingchip board presented properties similar to those of a conventionalfurniture chip board having a density of 700 kg/m³. This variant can beused when it is desired to reduce the weight of a product whilemaintaining the strength of the product.

The remaining technical values of the furniture chip board according tothe invention were at a level similar to those of an ordinary,conventional furniture chip board.

The invention can be varied in many ways without thereby deviating fromthe scope of the invention as expressed in the following claims.

1. A chip board including an intermediary layer (1) and a layer (2) oflarge chips positioned on both sides of said intermediary layer, as wellas optionally an outer layer (3) positioned on the outer surface of eachlayer of large chips, said layers, in addition to the chips, alsoincluding an adhesive, wherein the intermediary layer (1) consistsessentially of a mixture of wood chips having chip fractions of a chipsize of 0.1 to 20 mm, and that the chips of the intermediary layer (1)are randomly oriented, and the individual chip in the layer (2) of largechips presents the following characteristics: a length of approx. 50 toapprox. 130 mm, a width of approx. 4 to approx. 40 mm and a thickness ofapprox. 0.2 to approx. 2.0 mm, and wherein the chips within theindividual layer of large chips are all oriented in one and the samedirection.
 2. A chip board according to claim 1 wherein the intermediarylayer (1) includes a mixture of wood chips having chip fractions of achip size of 0.2 to 17 mm, and that the chips in the layer (2) of largechips are oriented in the longitudinal direction of the chip board.
 3. Achip board according to claim 1 wherein the individual chip of theindividual layer (2) of large chips presents the followingcharacteristics: a length of 70 to 120 mm, a width of 5 to 30 mm, and athickness of 0.2 to 2.0 mm.
 4. A chip board according to claim 1 whereinthe chips are kept together by 8 to 15% by weight of adhesive.
 5. Aprocess for producing a chip board according to claim 1 comprisingproducing said chip board by means of an intermittent press or by acontinuous pressing procedure at a temperature of 150.degree. C. to230.degree. C. and a pressure of 20 to 50 bars, the pressing periodbeing 5 to 15 seconds per mm of the thickness dimension of the chipboard.
 6. A chip board according to claim 1 comprising providing anouter layer (3) on the surface of each layer (2) of large chips, whereinthe outer layers include a chip mixture having chip fractions of a chipsize of 0.1 to 10 mm.
 7. A process for the preparation of chip boardsaccording to claim 1 comprising scattering different chip mixtures on apress plate, a wire, or a scatter band to form an intermediary layer, alayer of large chips positioned on both sides of said intermediarylayer, as well as outer layers positioned on the outer surface of thelayer of large chips, every chip of the intermediary layer (1) beingrandomly oriented during scattering while the chips of the individuallayer of large chips are oriented in one and the same direction duringthe scattering, said process further comprising compressing the layersat a temperature of 150 to 230.degree. C. and a pressure of 20 to 50bars, the pressing period being 5 to 15 seconds per mm of the thicknessdimension of the chip board.
 8. A process according to claim 7 furthercomprising compressing the components of the chip board to such anextent that the chip board achieves a density of 600 to 800 kglm.sup.3.9. A process according to claim 8 wherein the chip board achieves adensity of 650 to 750 kg/km.sup.3.
 10. A chip according to claim 3wherein the length is 80 to 110 mm, the width is 10 to 20 mm, and thethickness is 0.4 to 1.0 mm.
 11. A chip board according to claim 4wherein the chips are kept together by 10 to 13% by weight of adhesive.12. A chip board according to claim 4 wherein the adhesive comprises aurea-formaldehyde adhesive.
 13. A chip board according to claim 4wherein the adhesive comprises a melamine-urea formaldehyde adhesive.14. A chip board according to claim 4 wherein the adhesive comprises anisocyanate adhesive.
 15. A chip board according to claim 4 wherein theadhesive comprises a tannin adhesive.
 16. A chip board according toclaim 6 wherein the chip size is 0.1 to 5 mm.
 17. A process according toclaim 7 wherein the pressing period is 8 to 13 seconds.